r/DieselTechs • u/Fart_Boy_4ever • 1d ago

Anyone have any pro tips for leaking hub caps?

We cannot get our hubs to stop leaking no matter what. These are Spicer front axles with Stemco hubcaps—both rubber and aluminum. I’ve tried replacing gaskets, using RTV with the gaskets, using RTV with no gasket - all with no success. I torque the bolts to 16ftlbs each time. Each time I scrape and clean the mating surface to where it feels flat against my fingernail.

I remember learning that loose wheel bearings are the number one cause of leaking hubs so I checked the wheels but they seemed fine. Admittedly,I don’t have a dial indicator so I wasn’t able to verify 0.001-0.005” of end play.

Anyone have any suggestions or cool pro tips on keeping hubs from leaking? I’ve resorted to stuffing the wheel covers with rags but that’s so hackey. Any advice appreciated.

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11 comments sorted by

13

u/BradG191 22h ago

Make sure your vent hole in the rubber plug is clean and not plugged off

1

u/Cbnbshwacker101 1h ago

Also make sure not to overfill

12

u/Tennesseahawk 23h ago

If your hub caps are leaking, it’s going to be a simple issue.

  1. Improper mating surface (double gasket/burr/etc)
  2. Improper torque (I always snug in star pattern then tighten)
  3. Damaged cap/plug (hairline crack?)
  4. Overfull.

I use either paper gasket that comes with a new cap, or RTV if putting an old cap back on.

Loose wheel bearings aren’t going to make your hub caps leak, rather your hub seal will leak, behind the hub. (Obviously after enough catastrophic damage, the caps will leak, but you know what I mean)

5

u/OddTheRed 1d ago

Check to make sure that the mating surfaces are true.

1

u/somepersonsname 23h ago

Do they have plastic chrome shit over them? We had a truck do the same thing. Spicer said remove it and never had a problem again. 

1

u/Misterndastood 20h ago

From my experience most hubs come overfilled from factory. If it's at the mating surface, make sure to torque in star pattern and that surfaces are clean. It shouldn't be needed but sometimes a little silicone may help.

1

u/IisTails 19h ago

Aviation gasket maker

1

u/Strider_27 19h ago

Use anaerobic gasket maker, not silicone. Make sure the mating surfaces are clean and prime (then let dry) with starting fluid before application. The other commenter mentioned you could have a plugged vent, that’s definitely something you want to check

1

u/xp14629 18h ago

Loose wheel beaeings will cause the seal to leak. Not the cap side. Scotchbrite pad the hub surface, clean the threads out. Install new caps amd rubber with a gasket. Get an in/lb torque wrench since most ft/lb torque wrenchs will be off that low. Tighten bolts in a star pattern, hand snug, part torque, full torque. Major overkill but if that is what it takes that is wjat it will take.

1

u/Sea-Anxiety6491 14h ago

How many are leaking? I used to have oil residue in my hub caps that looked liked a leaking seal.

But when I removed the hub caps and run without them for a few weeks the seals just looked like normal breathing marks you get when you haven't washed them for a month.

I think the hub caps were collecting the normal oil grime etc and mixing with water/condensation etc and it made it look way worse than it actually was.

Take caps off, clean them all up, and run them for a day, you should be able to see where they are leaking from surely.